1. Field of the Invention
The present invention relates to an elastomer composition for use in improving impact strength of plastic materials. More particularly, the present invention relates to an elastomer composition comprising chemically modified ethylene-α-olefin elastomer, a method of producing the composition and a method of improving impact strength of plastic materials.
2. Description of the Prior Art
EP(D)M rubber, a kind of ethylene-α-olefin elastomer copolymers, has been extensively used to improve the impact strength of polyolefin products, especially, low-temperature impact strength by taking advantage of its high compatibility with polyolefin resins.
On the other hand, EP(D)M rubber is poor in its compatibility with a polar plastics because of its non-polar characteristics, so its application range is limited. For example, EP(D)M cannot be sufficiently blended with such general-purpose engineering plastics as nylon, ABS (acrylonitrile butadiene styrene), polycarbonate, etc. To expand its applicability to such polar engineering plastics, EP(D)M rubber is made polar through provision with polar groups with the use of, for example, maleic acid. Typically, EP(D)M is made compatible with thermoplastics such as polyamides by being grafted with carbonyl derivatives.
Recently, the automobile industry has paid special attention to thermoplastics, especially polyamides, as substitutes for metallic parts for automobiles. For use in automobile parts, thermoplastics are formed into high molecular weight thermoplastic elastomers by injection molding. On the whole, the applicability of thermoplastics is limited by processing methods. Being low in melt strength, polyamide, for example, frequently undergoes parison tearing that leads to failures in blow molding.
There is required a thermoplastic modifier that is easily dispersed without increasing the viscosity of the blend. Because they are easily dispersed in thermoplastic elastomers, high molecular weight modifiers may be used to increase the melt strength of elastomers. In addition, high molecular weight modifiers do not increase the viscosity of the blend or limit the period time of the blow-molding phase. Therefore, there remains a need for EP(D)M rubber, which is modifier to blend the thermoplastics without reducing the melt viscosity of the final EP(D)M/thermoplastic blend. Modified with typical modifiers, the EP(D)M rubber is improved in its compatibility with plastics and thus can be used as an impact reinforcement to increase the impact strength of the plastics at room temperature as well as at low temperatures.
Conventionally, EP(D)M rubber has its appearance limited to pellets in order to be modified within extruders. The pelletization of EP(D)M requires that it contain an ethylene content of 70 wt % or more. However, higher ethylene contents bring about lesser improvements in impact strength. Particularly, the EP(D)M rubber with high ethylene contents cannot act as modifiers, resulting in a drastic decreases in low temperature impact strength.